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Heme-binding characteristics of the isolated PAS-B domain of mouse Per2, a transcriptional regulatory factor associated with circadian rhythms.
MedLine Citation:
PMID:  20887817     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
Mouse period homolog 2 (mPer2), an important transcriptional regulatory factor associated with circadian rhythms, is composed of two N-terminal PAS (PAS-A and PAS-B) domains and a C-terminal domain. The PAS-A domain of mPer2 binds the heme iron via a Cys axial ligand. A corresponding transcriptional regulatory factor, neuronal PAS 2 protein (NPAS2), also contains PAS-A and PAS-B domains at the N-terminus with heme-binding capability. In particular, the PAS-B domain appears important for protein-protein interactions critical for transcriptional regulation. In the present study, we examined the heme-binding characteristics of the isolated PAS-B domain of mPer2. Our experiments show that the Fe(III) heme binds the isolated PAS-B domain with a heme to protein stoichiometry of 1:1. The Fe(III) protein complex is suggested to consist of an admixture of 6-coordinated His-bound high-spin and low-spin complexes. Marked pH-dependent spectral changes were observed, in contrast to the spectrum of the Fe(III) bound PAS-A domain of mPer2, which appeared pH-resistant. Treatment with diethylpyrocarbonate abolished the heme-binding ability of this protein, supporting the proposal that His is the axial ligand. Heme dissociation was composed of two phases with rate constants of 4.3×10(-4)s(-1) (50%) and 4.0×10(-3)s(-1) (50%), which were markedly higher than that (1.5×10(-7)s(-1)) of the prototype heme protein, myoglobin. The Soret CD band of the H454A PAS-B mutant was significantly different from those of wild-type and other His mutant proteins, strongly suggesting that His454 is one of the axial ligands for the Fe(III) complex.
Authors:
Koya Hayasaka; Kenichi Kitanishi; Jotaro Igarashi; Toru Shimizu
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Publication Detail:
Type:  Journal Article     Date:  2010-09-29
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1814     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  2011 Feb 
Date Detail:
Created Date:  2011-01-10     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  326-33     Citation Subset:  IM    
Copyright Information:
Copyright © 2010 Elsevier B.V. All rights reserved.
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